本文主要讲述javaWeb的请求转发和请求重定向的区别
一. 请求转发
1. 图解
2. 代码示例
Servlet1的代码示例如下
public class Servlet1 extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
System.out.println("Servlet1收到请求");
req.setAttribute("key","Servlet1盖的章");
req.getRequestDispatcher("/servlet2").forward(req,resp);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
}
}
Servlet2的代码示例如下
public class Servlet2 extends HttpServlet {
@Override
// 请求转发，处理的是同一个请求
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
Object key = req.getAttribute("key");
System.out.println("Servlet2收到了" + key);
resp.getWriter().write("Servlet2响应的内容");
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
}
}
浏览器收到响应，显示结果如下
思考1
响应response没有设置编码规则，导致默认的编码规则不支持中文字符，验证如下
public class Servlet2 extends HttpServlet {
@Override
// 请求转发，处理的是同一个请求
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
Object key = req.getAttribute("key");
System.out.println("Servlet2收到了" + key);
System.out.println(resp.getCharacterEncoding());
resp.getWriter().write("Servlet2响应的内容");
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
}
}
tomcat日志如下
Servlet1收到请求 Servlet2收到了Servlet1盖的章 ISO-8859-1
由此看出，字符集是ISO-8859-1应该不支持中文字符
将resp的字符集设置为utf-8，声明如下
resp.setCharacterEncoding("utf-8");
浏览器收到响应，显示结果如下，仍是乱码
思考2
resp响应设置了字符集utf-8，但是浏览器编码格式不是utf-8，而是windos-1252。字符集不相同，导致乱码
由思考和思考2，引出问题：如何保证浏览器和响应resp的字符集相同呢？
首先介绍Content-Type
解决方法
Servlet2声明如下
public class Servlet2 extends HttpServlet {
@Override
// 请求转发，处理的是同一个请求
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
Object key = req.getAttribute("key");
System.out.println("Servlet2收到了" + key);
// 解决浏览器与resp响应的编码格式不一致问题：
// 方式一:
resp.setHeader("Content-Type","text/html;charset=utf-8");
// 方式二:
resp.setContentType("text/html;charset=utf-8");
resp.getWriter().write("Servlet2响应的内容");
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
}
}
3. 总结
① 请求转发，一直是同一个请求【请求的数据可以共享】
② 在resp响应浏览器内容时，如果有中文字符，则在响应之前，需要设置content-type，即 resp.setContentType("text/html;charset=utf-8");
二. 请求重定向
1. 图解
2. 代码示例
Servlet1的代码示例如下
public class Servlet1 extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
System.out.println("Servlet1收到请求");
System.out.println("Servlet1请求重定向给Servlet2");
resp.sendRedirect("/servlet2");
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
}
}
Servlet2的代码示例如下
public class Servlet2 extends HttpServlet {
@Override
// 请求转发，处理的是同一个请求
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
System.out.println("Servlet2收到请求");
System.out.println("请求路径为: ");
StringBuffer requestURL = req.getRequestURL();
System.out.println(requestURL);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
}
}
浏览器收到响应，结果如下
思考
请求重定向的路径写的不对，下面解释一下 " / "
在浏览器中，" / "是指 http://localhost:8080，即http://ip地址:端口号
在web项目中，" / "是指http://localhost:8080/javaWeb03，即http://ip地址:端口号/项目名称
解决方法
Servlet1声明如下
public class Servlet1 extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
System.out.println("Servlet1收到请求");
System.out.println("Servlet1请求重定向给Servlet2");// 解决方式1：相对路径
resp.sendRedirect("/javaWeb02/servlet2");
// 解决方式2：绝对路径
resp.sendRedirect("http://localhost:8080/javaWeb02/servlet2");
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
}
}
tomcat日志结果如下
Servlet1收到请求 Servlet1请求重定向给Servlet2 Servlet2收到请求 请求路径为: http://localhost:8080/javaWeb02/servlet2
3. 总结
① 注意浏览器和web项目中的" / "的不同含义；
② 请求重定向是浏览器向服务器发了两次请求
标签：Servlet2,请求,ServletException,Servlet1,resp,req,转发,javaWeb03 From： https://www.cnblogs.com/zwgitOne123/p/17111194.html